Thermoluminescence of calcium phosphate co-doped with gadolinium and praseodymium

The thermoluminescence of beta-irradiated Ca₅(PO₄)₃OH:Gd³⁺,Pr³⁺ is reported. A glow-curve measured at 5 °C s^-1 after beta irradiation to 12 Gy revealed an apparently single wide peak at 88°C. The natural thermoluminescence also showed a single peak with an expanse of over 400°C. Analysis of the glow-peak after laboratory irradiation using the partial heating procedure T_m-T_stop and its dependence on irradiation was suggestive of the peak being made up of an overlap of closely spaced ones. At least 10 closely collocated components were experimentally recovered using a combination of partial heating and digital mustering. Kinetic analysis of the first three prominent peaks I, II, III using glow-curve deconvolution showed their activation energies to be 0.78 ± 0.01 eV, 0.95 ± 0.01 eV and 1.07 ± 0.01 eV, respectively, and the corresponding frequency factor to be of the order of 10¹⁰, 10¹² and 10¹³ s^-1 in that order. Complementary analysis using the initial-rise and variable heating rate methods gave similar values for the trap depth. The dose-dependence of the main unresolved peak over the range 6-185 Gy was determined as supralinear using the superlinearity and supralinearity indices.